1.2. Technical Overview

This chapter contains an overview of HAFS prerequisites, HAFS repository management and structure, workflow design, and HAFS v2.0 operational updates.

1.2.1. Prerequisites for Working with the HAFS Repository

• Git version 1.8.2 or newer, which added the possibility to track branches of submodules. The following versions of Git are used on NOAA HPCs:

  • Orion:

    • Git version 1.8.3.1 (system default)

    • Git version 2.21.0 (available via module load git/2.21.0)

  • Jet/Hera: Git version 2.18.0

  • WCOSS Dell: Git version 1.8.3.1

  • WCOSS Cray (cannot access GitHub)

    • Git version 1.7.12.4 (system default)

    • Git version 2.14.2 (available)

      • module use /gpfs/hps3/emc/hwrf/noscrub/soft/modulefiles

      • module load git/2.14.2

• GitHub account (e.g., FirstLast-NOAA)

1.2.2. HAFS GitHub Repository Management

The authoritative HAFS repository is publicly available on GitHub at: https://github.com/hafs-community/HAFS. It is maintained by EMC and DTC with developments and contributions from the UFS HAFS application team and the hurricane research community.

HAFS Branching/Tagging Conventions:

• develop: The main development branch

• support/[name]: Branches used by operational implementations or HFIP real-time parallel experiments (e.g., support/hafs.v0.2.0)

• release/vx.x.x: Public release branches (e.g., release/v1.0.0)

• [name].v#.#.# (tags): hafs.v0.2.0, hafs.v1.0.0, public.v1.0.0, etc.

• hotfix/[name]: Temporary bug fix branches

• feature/[name]: Feature branches for adding new capabilities or enhancements

The HAFS repository only hosts major feature branches (e.g., feature/hafs_nesting) that require active group collaborations. Individual developers can work on feature branches in their personal HAFS forks.

Fig. 1.1 Example HAFS Branching Diagram

1.2.3. HAFS Directory Structure

The following shows the names of the files and directories in the HAFS repository.

1.2.4. HAFS Submodules

HAFS contains the following subcomponents:

1.2.5. HAFS Workflow Schematic

1.2.6. HAFS v2.0.0 Operational Updates

Model: Hurricane Analysis and Forecast System (HAFS)

Version: hafs.v2.0.0

Released: July 01, 2024, 1200UTC

Location on GitHub: HAFS GitHub Repository

Clone the repository:

git clone -b production/hafs.v2 --recursive  https://github.com/hafs-community/HAFS.git

Attention

HAFSv2 runs in production on WCOSS2; pre-implementation testing was performed on Hera and Orion. It is likely possible to run on other systems, but additional code modifications may be required to run an experiment, and this capability has not yet been tested.

Purpose:

• The HFSA configuration provides hurricane track and intensity forecast guidance to 5.25 days over all global oceanic basins, including NATL, EPAC, CPAC, WPAC, NIO, and SH basins.

• The HFSB configuration provides hurricane track and intensity forecast guidance for 5.25 days over NHC/CPHC basins, including NATL, EPAC, CPAC basins.

Developed by:

EMC and the UFS Hurricane Application Team. See active HAFSv2 developers in Table 1.1.

Table 1.1 HAFS Developers

Area of Expertise	Institution	Developers
Atmospheric model dynamics/configurations/workflow	NCEP/EMC	Bin Liu, Dusan Jovic, Avichal Mehra, JungHoon Shin, Vijay Tallapragada, Biju Thomas, Jun Wang, Zhan Zhang, Yangxing Zheng
Atmospheric model dynamics/configurations/workflow	AOML/HRD	Ghassan Alaka, S. Gopalakrishnan, William Ramstrom, Xuejin Zhang
Atmospheric model dynamics/configurations/workflow	DTC	Mrinal Biswas, Kathryn Newman, Linlin Pan
Atmospheric model dynamics/configurations/workflow	GFDL	Rusty Benson, Lucas Harris, Joseph Mouallem
Atmospheric model dynamics/configurations/workflow	GSL	Samuel Trahan
Ocean/Wave coupling through CMEPS	NCEP/EMC	Maria Aristizabal, Bin Li, Matthew Masarik, Jessica Meixner, John Steffen
Ocean/Wave coupling through CMEPS	AOML/HRD	Lew Gramer
Ocean/Wave coupling through CMEPS	AMOL/PhOD	HeeSook Kang, Hyun-Sook Kim, Ming Ming Shao
Ocean/Wave coupling through CMEPS	NCAR/ESMF	Dan Rosen, Gerhard Theurich, Ufuk Turuncoglu, Ann Tsay
Data Assimilation	NCEP/EMC	Jing Cheng, Daryl Kleist, Ting Lei, Shun Liu, Xu Lu, Yonghui Weng, Sho Yokota
Data Assimilation	AOML/HRD	Sarah D. Ditchek, Jason Sippel
Data Assimilation	OU	Xuguang Wang
Data Assimilation	UM/CIMAS	Altug Aksoy, Dan Wu
Data Assimilation	UMD	Joseph Knisely, Kenta Kurosawa, Jonathan Poterjoy
Data Assimilation	SUNY/U at Albany	Ryan Torn, Eun-Gyeong Yang
Model Pre- and Post-processes	NCEP/EMC	George Gayno, Hui-Ya Chuang, Nathalie Rivera-Torres, Qingfu Liu, Chuan-Kai Wang, Wen Meng, Lin Zhu
Model Pre- and Post-processes	GFDL	Timothy Marchok
Atmospheric Physics	NCEP/EMC	Jongil Han, Ruiyu Sun, Xu Li, Weiguo Wang, Fanglin Yang
Atmospheric Physics	AOML/HRD	Andrew Hazelton
Atmospheric Physics	UAH	Xiaomin Chen
Atmospheric Physics	PSL	Lisa Bengtsson
Verification/Evaluation	NCEP/EMC	Olivia Ostwald, Hananeh Jafary, Jiayi Peng
Verification/Evaluation	NHC	Michael Brennan, Jon Martinez, Ben Trabing, David Zelinsky, Wallace Hogsett, Jamie Rhome, Richard Pasch
Verification/Evaluation	JTWC	Brian Strahl, Levi Cowan

1.2.6.1. Input/Output

Input Data:

• Global Forecast System (GFS, including GFS/GDAS) NetCDF format analysis for atmospheric initial conditions and 3-hourly GRIB2 files (up to 129 h) for atmospheric lateral boundary conditions and atmospheric forcing for oceanic and wave model components.

• Global RTOFS files for oceanic initial and boundary conditions for MOM6 and HYCOM.

• GFS/GDAS global wave analysis/forecast files for HFSA wave component initial and lateral boundary conditions.

• OBSPROC observational data for HAFS data assimilation.

Input DCOM Dependencies The following scripts require input files from DCOM (data input) directory:

• ./scripts/exhafs_obs_prep.sh: To decode/dump TDR/HDOB/TEMPDROP data

• ./scripts/exhafs_msg_check.py: To check the message files are properly created by checking the original NHC/JTWC message files in the DCOM directory.

• ./ush/setup_hurricane: For SDM to set up hurricane message files by extracting info from the original NHC/JTWC message files in the DCOM directory.

Output:

• ATCF track forecast files, 4x/day at 00Z/06Z/12Z/18Z

1.2.6.2. Locations for Output

• WCOSS2:

  • HFSA: /lfs/h1/ops/prod/com/hafs/v2.0/hfsa.yyyymmdd/hh

  • HFSB: /lfs/h1/ops/prod/com/hafs/v2.0/hfsb.yyyymmdd/hh

• Other servers:

  • NCEP ftp server, NOMADS, NWS Gateway/SBN

  • See NOMADS here.

1.2.6.3. Background

HAFSv2 will replace NCEP’s current operational hurricane forecast systems, HAFSv1 in the 2024 hurricane season. The upgraded system will provide improved and comparable tropical cyclone track and intensity forecast guidance in all global oceanic basins, as demonstrated through evaluation of retrospective and real time experiments compared against the two current configurations of operational HFSAv1 and HFSBv1.

1.2.6.4. Scientific Changes to Improve Track and Intensity Forecast Skills

System and Infrastructure Upgrades:

• Updated version of hafs-community/ufs-weather-model, HAFSv2 final scientific configuration freeze on 02/08/2024.

• Increase moving nesting horizontal resolution from 6-2 km to 5.4-1.8 km (HFSA only).

• Reduce model time step from 90 to 72s (HFSB only).

• Updated horizontal advection options.

• Improved model stability and runtime efficiency.

Vortex Initialization Improvement:

• Enhance vortex initialization to cycle hydrometeor variables and vertical velocity (HFSA only).

• Update composite vortex and reduce warm-cycling Vmax threshold from 50 to 40 kt (HFSA only).

Data Assimilation (DA) Improvement:

• Ingest new high-resolution GOES-R mesoscale AMVs.

• Scale-Dependent Localization for inner core data assimilation.

• Refine GPS Radio Occultation (RO) DA.

Model Physics Advancement:

• Upgrade Thompson MP with bug fixes.

• Thompson Microphysics for NATL basin, GFDL Microphysics for EPAC/CPAC and JTWC basins (HFSA only).

• Update TKE EDMF PBL and SASAS CP schemes with vertical wind shear impacts.

• Change the radiation calling time step from 720s to 900s (HFSA only).

• Reduce radiation time step from 1800 to 720s (HFSB only).

• Update CO2 fix files.

Ocean/Wave Coupling:

• MOM6 ocean model coupling (HFSA only).

• CMEPS with inline-CDEPS coupling (HFSA only).

Post-processing:

• Upgrade GFDL Tracker.

Software Dependencies:

• See list of dependencies here.

Output Changes:

• New variables in HAFSv2: No

• Removed variables: No

1.2.6.5. Computer Resource Information

Computation resource updates:

• HAFSv2 will use similar computing resources as HAFSv1.

• HAFS Weather Model (HWM): No significant node increase expected for the forecast job.

List of the module versions used in HAFS:

• See list of module version here.

Data retention for files in:

• /lfs/h1/ops/prod/com/hafs/v2.0/hfsa.yyyymmdd/hh and /lfs/h1/ops/prod/com/hafs/v2.0/hfsb.yyyymmdd/hh

  • Disk space usage: Increased from 145/140 GB (HFSAv1/HFSBv1) per cycle to ~295/195 GB (HFSAv2/HFSBv2).

  • HPSS disk requirement: Increased from ~142/126 GB (HFSAv1/HFSBv1) to ~228/133 GB (HFSAv2/HFSBv2).

  • Preferred data retention in COM: Files to be kept for 7 days.

1.2.6.6. Pre-Implementation Testing

All changes have been tested successfully using available input from Table 1.2.

Table 1.2 Test Objectives and Comments

Test Objective	Comment
Test two consecutive cycles for one storm in each global basin	Basic tests for each basin
Very weak storm (<8 m/s)	Use GFS analysis as input (No VI/DA)
Missing ICs from GDAS data	HAFS fails with proper error message
Missing BCs from GFS data	HAFS fails with proper error message
Missing previous cycle’s 6-hr forecast output	HAFS runs to completion in cold start mode
Zero length data files for GSI	Initialization and analysis runs to completion
Missing input data files for GSI	Initialization and analysis runs to completion
Failed ocean initialization	HAFS runs in un-coupled mode
Tracker fails to identify initial storm location	Swath generator fails with proper error message
Cross dateline and Greenwich tests	Ensure HAFS model and scripts properly handle the specific situations
Bugzilla Entries	Operational failure

NHC, CPHC, and JTWC were suggested to evaluate model products and MAG was suggested to evaluate GEMPAK files.

1.2.6.7. Dissemination and Archiving

Dissemination Information: Files were disseminated as follows:

• ATCF files to NHC (and CPHC for Central Pacific Basin storms) and JTWC (for all global basins, including SH basins)

• GRIB files to NOMADS

• GEMPAK files to MAG

All the files in the COM directory should be transferred from PROD WCOSS2 to DEV WCOSS2. None of the code is proprietary, and there is no restricted data.

Archive to HPSS: All the files in the COM directory are preferred to be archived in 5-year retention HPSS directory.